Image sensors have become ubiquitous. They are widely used in digital devices such as still cameras, cellular phones, video cameras, as well as, medical, automobile, security, and other applications. The technology used to manufacture image sensors has continued to advance at a great pace. For example, the demands of higher resolution and lower power consumption have encouraged the further miniaturization and integration of these devices.
The typical image sensor operates as follows. Image light from an external scene is incident on the image sensor. The image sensor includes a plurality of photosensitive elements such that each photosensitive element absorbs a portion of incident image light. Photosensitive elements included in the image sensor, such as photodiodes, each generate image charge upon absorption of the image light. The amount of image charge generated is proportional to the intensity of the image light. The generated image charge may be used to produce an image representing the external scene.
However, as the miniaturization of image sensors progresses, defects within the image sensor architecture become more readily apparent and may reduce the image quality of the image. For example, excess current leakage within certain regions of image sensor may cause high dark current, sensor noise, white pixel defects, and the like. These defects may significantly deteriorate the image quality from the image sensor, which may result in reduced yield and higher production costs.
Corresponding reference characters indicate corresponding components throughout the several views of the drawings. Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention.